Refactor to remove ram2

Both main and auxiliary memory need to keep an extra 4k of memory that
is bank-switchable, so we have changed to store that memory literally
within the main and aux segments.

include/apple2.h

@@ -115,15 +115,6 @@ typedef struct {
      */
     vm_segment *rom;
     
-    /*
-     * Additionally, the Apple II had a standalone block of RAM (with no
-     * good name for it, really, hence the regrettably vague "ram2") so
-     * that you technically could use 16k of RAM from a set of 12k
-     * addresses. The extra 4k lives a lonely life in the garage
-     * apartment.
-     */
-    vm_segment *ram2;
-
     /*
      * The Apple II may have an auxiliary RAM bank; this was possible by
      * installing a card there. If you had the 80-column text card (and

include/apple2.mem.h

@@ -4,6 +4,16 @@
 #include "apple2.h"
 #include "vm_segment.h"
 
+/*
+ * The MOS 6502 expects 64k of addressable space, but the Apple II
+ * technically has 68k of memory in each bank. (Along with having both a
+ * main and an auxiliary memory bank, with identical address schemes.)
+ * This is handled through bank-switching; the additional memory (which
+ * is accessible through $D000 - $DFFF) is actually stored in the
+ * 64k-68k block at the end.
+ */
+#define APPLE2_MEMORY_SIZE 0x11000
+
 /*
  * Given a slot number (1-7), this will return the memory page address
  * for the site of the ROM that is associated for the peripheral that
@@ -34,11 +44,6 @@
  */
 #define APPLE2_ROM_SIZE 0x3000
 
-/*
- * Whereas the second bank of RAM is a mere 4k
- */
-#define APPLE2_RAM2_SIZE 0x1000
-
 /*
  * At the highest point (with the IIe extended 80 column text card), you
  * could have a whole other 64k of data in auxiliary memory. (Of which

src/apple2.c

@@ -45,14 +45,14 @@ apple2_create(int width, int height)
     // Forward set these to NULL in case we fail to build the machine
     // properly; that way, we won't try to free garbage data
     mach->rom = NULL;
-    mach->ram2 = NULL;
+    mach->aux = NULL;
     mach->main = NULL;
     mach->sysfont = NULL;
     mach->screen = NULL;
     mach->drive1 = NULL;
     mach->drive2 = NULL;
 
-    mach->main = vm_segment_create(MOS6502_MEMSIZE);
+    mach->main = vm_segment_create(APPLE2_MEMORY_SIZE);
     if (mach->main == NULL) {
         log_critical("Could not initialize main RAM!");
         apple2_free(mach);
@@ -74,10 +74,9 @@ apple2_create(int width, int height)
 
     // Initliaze our system ROM and separate bank-switched block of RAM
     mach->rom = vm_segment_create(APPLE2_ROM_SIZE);
-    mach->ram2 = vm_segment_create(APPLE2_RAM2_SIZE);
+    mach->aux = vm_segment_create(APPLE2_MEMORY_SIZE);
-    mach->aux = vm_segment_create(APPLE2_AUX_SIZE);
+    if (mach->rom == NULL || mach->aux == NULL) {
-    if (mach->rom == NULL || mach->ram2 == NULL || mach->aux == NULL) {
+        log_critical("Could not initialize ROM / AUX!");
-        log_critical("Could not initialize ROM / RAM2 / AUX!");
         apple2_free(mach);
         return NULL;
     }
@@ -260,10 +259,6 @@ apple2_free(apple2 *mach)
         vm_segment_free(mach->rom);
     }
 
-    if (mach->ram2) {
-        vm_segment_free(mach->ram2);
-    }
-
     if (mach->main) {
         vm_segment_free(mach->main);
     }

src/apple2.mem.c

@@ -22,13 +22,14 @@ SEGMENT_READER(apple2_mem_read_bank)
         return vm_segment_get(mach->rom, addr - APPLE2_BANK_OFFSET);
     }
 
-    // If the address is $D000..$DFFF, then we may need to get the byte
+    // Each memory bank (main or auxiliary) have an additional 4k of RAM
-    // from the ram2 bank. 
+    // that you can access through bank-switching in the $D000 - $DFFF
+    // range, which is actually held at the _end_ of memory beyond the
+    // 64k mark.
     if (addr < 0xE000 && mach->bank_switch & MEMORY_RAM2) {
         // The same caution holds for getting data from the
         // second RAM bank.
-        return vm_segment_get(mach->ram2, 
+        return segment->memory[addr + 0x3000];
-                              addr - APPLE2_BANK_OFFSET);
     }
 
     // Otherwise, the byte is returned from bank 1 RAM, which is the
@@ -58,11 +59,11 @@ SEGMENT_WRITER(apple2_mem_write_bank)
     // time--well, nearly the same time, considering the 6502 does not
     // allow parallel actions!
 
-    // If bank 2 RAM is turned on, and the address is in the $D000
+    // In this case, we need to assign the value at the 64-68k range at
-    // hexapage, then we write to our ram2 segment.
+    // the end of memory; this is just a simple offset from the given
+    // address.
     if (addr < 0xE000 && mach->bank_switch & MEMORY_RAM2) {
-        vm_segment_set(mach->ram2,
+        segment->memory[addr + 0x3000] = value;
-                       addr - APPLE2_BANK_OFFSET, value);
         return;
     }
 

tests/apple2.mem.c

@@ -54,14 +54,15 @@ Test(apple2_mem, read_bank)
     vm_segment_set(mach->main, 0xD077, val);
     cr_assert_eq(vm_segment_get(mach->main, 0xD077), val);
     cr_assert_neq(vm_segment_get(mach->rom, 0x77), val);
-    cr_assert_neq(vm_segment_get(mach->ram2, 0x77), val);
+    cr_assert_neq(vm_segment_get(mach->main, 0x10077), val);
 
     // Finally, in RAM2 bank mode, we test similarly to ROM mode. Set
-    // the value directly in ram2 and see if it's there when addressing
+    // the value directly in ram2 (which is at $10000 - $1FFFF) and see
-    // from main memory.
+    // if it's there when addressing from main memory in the $Dnnn
+    // range.
     val = 111;
     apple2_set_bank_switch(mach, mach->bank_switch | MEMORY_RAM2);
-    vm_segment_set(mach->ram2, 0x77, val);
+    vm_segment_set(mach->main, 0x10077, val);
     cr_assert_eq(vm_segment_get(mach->main, 0xD077), val);
 }
 
@@ -91,18 +92,18 @@ Test(apple2_mem, write_bank)
     wrong = 232;
     apple2_set_bank_switch(mach, MEMORY_WRITE);
     vm_segment_set(mach->main, 0xD078, right);
-    vm_segment_set(mach->ram2, 0x78, wrong);
+    vm_segment_set(mach->main, 0x10078, wrong);
     cr_assert_eq(vm_segment_get(mach->main, 0xD078), right);
-    cr_assert_eq(vm_segment_get(mach->ram2, 0x78), wrong);
+    cr_assert_eq(vm_segment_get(mach->main, 0x10078), wrong);
 
     // RAM2 is most of the 64k, except the first 4k of the last 12
     // ($D000..$DFFF) is in ram2.
     right = 210;
     wrong = 132;
     apple2_set_bank_switch(mach, mach->bank_switch | MEMORY_RAM2);
-    vm_segment_set(mach->ram2, 0x73, wrong);
+    vm_segment_set(mach->main, 0x10073, wrong);
     vm_segment_set(mach->main, 0xD073, right);
-    cr_assert_eq(vm_segment_get(mach->ram2, 0x73), right);
+    cr_assert_eq(vm_segment_get(mach->main, 0x10073), right);
 }
 
 Test(apple2_mem, init_disk2_rom)